It is desirable that a cushion that persons lay down thereon has characteristics best suited to each individual depending on height, weight, figure and posture during sleeping of the person. However, especially in the case of a spring mattress, to adapt cushion characteristics of any area on the mattress surface to each individual, production becomes difficult and takes too long time and therefore, under present circumstances, customization of the mattress has not been spread like customization of clothes.
This is because priority is given to the convenience for manufacturers of mass producing the same type of mattresses and improving the production efficiency and an apparatus and a method for producing a mattress for customization have not been considered so far.
Even if such an apparatus or a method was considered, under present circumstances, the production efficiency is poor. Any attempt for supporting the customization has not been made so far because of the following problems, for example: attempting to support customization by optionally combining two or more kinds of coils having different wire diameters requires at least two coiling machines, which leads to excessively high equipment expenses; while it is possible to manufacture the coils having different wire diameters using a single machine, this reduces productive efficiency because it takes long to adjust for switching the coiling machine, and increases the cost because manual labor for setting of a spring sheet as well as more space for the stock for each type of coils are required
However, while people do not put on the same clothes every day, people spend on contacting the same bedclothes for at least several hours every day. In consideration of this, it is considered that customization of the mattress is a very important problem and that users' demand for the customization has increased.
For this reason, it has been devised that customization is achieved for almost the same production time of conventional mattresses by optionally combining coil springs having different elasticity to produce the spring sheet, controlling heat treatment time due to electrification for removing stress after coiling and forcibly applying external force after coiling to change winding pitch of the coils. Indeed, in an initial phase, such mattresses have an advantage that they exhibit elastic performances having different repulsive forces, but with use frequency and time passage, the elastic performances converge on a certain elastic performance and are changed to a uniform elasticity.
Furthermore, although it is considered that one coiling machine forms coil springs having different repulsive forces by coiling coil springs having the same wire diameter with the winding pitch of the coils being changed from the beginning, to increase repulsive force of the coil springs having the same wire diameter, it is necessary to make winding diameter of the coil spring smaller and make winding pitch larger without changing the number of windings. In this case, there results in unstable coil shape with a small winding diameter and a large coil length and due to a large angle of instability, weakening during use becomes larger, the coil spring is easy to break and there occurs a problem of durability. Thus, there is a limit to make discrimination in repulsive force and a large difference in repulsive force cannot be generated (Unexamined Patent Publication No. H11-253278 and Unexamined Patent Publication No. 2000-41792).
A problem to be solved is to address customization of a spring mattress as needs of the user by producing a spring sheet (pocket coil sheet) in units of rows corresponding to vertical rows or horizontal rows of the mattress and arranging coil springs having different wire diameters within the rows in a pattern.